Field of the Invention
The present invention relates to a semiconductor optical modulation device including a semiconductor optical modulator modulating an optical signal based on an electrical signal, and in particular to a semiconductor optical modulation device capable of improving the frequency response characteristic.
Background Art
For a semiconductor optical modulation device in which a transmission line part in a metal stem part having a lower impedance is connected to a semiconductor optical modulator and a resistor connected in parallel to each other, and in which a flexible substrate is connected to the transmission line part, adding a line having an impedance lower than a matching impedance to a portion of a transmission line on the flexible substrate for the purpose of limiting the influence of multiple reflection and improving a frequency response characteristic has been proposed (see, for example, Japanese Patent Laid-Open No. 2012-230176). Connecting a series circuit of a resistor and a capacitor between differential signal lines on a flexible substrate for the purpose of improving a frequency response characteristic has also been proposed (see, for example, Japanese Patent Laid-Open No. 2005-286305).